linux-kernel - Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned

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Message-ID: <87pqdh1mvs.fsf@caffeine.danplanet.com>
Date:	Tue, 14 Feb 2012 06:59:51 -0800
From:	Dan Smith <danms@...ibm.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned

DR> That's not a precedent, there's a big difference between the
DR> performance of gup_fast(), where we can't spare an additional
DR> compare and branch, and walk_page_range().  VM_BUG_ON() is typically
DR> used in situations where a debug kernel has been built, including
DR> CONFIG_DEBUG_VM, and the check helps to isolate a problem that would
DR> be otherwise difficult to find.

Okay, fair enough. I was trying to stay in line with the other
conventions, knowing that the check would only be done with
CONFIG_DEBUG_VM enabled.

I'd rather just make it always do the check in walk_page_range(). Does
that sound reasonable?

-- 
Dan Smith
IBM Linux Technology Center
email: danms@...ibm.com
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